draft-ietf-ipv6-2461bis-10.txt   draft-ietf-ipv6-2461bis-11.txt 
INTERNET-DRAFT T. Narten, INTERNET-DRAFT T. Narten,
Expires: June 2007 IBM Expires: September 2007 IBM
Obsoletes: 2461 (if approved) E. Nordmark, Obsoletes: 2461 (if approved) E. Nordmark,
Sun Microsystems Sun Microsystems
W. Simpson, W. Simpson,
Daydreamer Daydreamer
H. Soliman, H. Soliman,
Elevate Technologies Elevate Technologies
January, 2007 March, 2007
Neighbor Discovery for IP version 6 (IPv6) Neighbor Discovery for IP version 6 (IPv6)
<draft-ietf-ipv6-2461bis-10.txt> <draft-ietf-ipv6-2461bis-11.txt>
Status of this memo Status of this memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document specifies the Neighbor Discovery protocol for IP This document specifies the Neighbor Discovery protocol for IP
Version 6. IPv6 nodes on the same link use Neighbor Discovery to Version 6. IPv6 nodes on the same link use Neighbor Discovery to
discover each other's presence, to determine each other's link-layer discover each other's presence, to determine each other's link-layer
addresses, to find routers and to maintain reachability information addresses, to find routers and to maintain reachability information
about the paths to active neighbors. about the paths to active neighbors.
Table of Contents Table of Contents
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5.3. Garbage Collection and Timeout Requirements...............34 5.3. Garbage Collection and Timeout Requirements...............34
6. ROUTER AND PREFIX DISCOVERY....................................35 6. ROUTER AND PREFIX DISCOVERY....................................35
6.1. Message Validation........................................36 6.1. Message Validation........................................36
6.1.1. Validation of Router Solicitation Messages...........36 6.1.1. Validation of Router Solicitation Messages...........36
6.1.2. Validation of Router Advertisement Messages..........36 6.1.2. Validation of Router Advertisement Messages..........36
6.2. Router Specification......................................37 6.2. Router Specification......................................37
6.2.1. Router Configuration Variables.......................37 6.2.1. Router Configuration Variables.......................37
6.2.2. Becoming An Advertising Interface....................41 6.2.2. Becoming An Advertising Interface....................41
6.2.3. Router Advertisement Message Content.................42 6.2.3. Router Advertisement Message Content.................42
6.2.4. Sending Unsolicited Router Advertisements............43 6.2.4. Sending Unsolicited Router Advertisements............43
6.2.5. Ceasing To Be An Advertising Interface...............44 6.2.5. Ceasing To Be An Advertising Interface...............43
6.2.6. Processing Router Solicitations......................44 6.2.6. Processing Router Solicitations......................44
6.2.7. Router Advertisement Consistency.....................45 6.2.7. Router Advertisement Consistency.....................45
6.2.8. Link-local Address Change............................46 6.2.8. Link-local Address Change............................46
6.3. Host Specification........................................47 6.3. Host Specification........................................47
6.3.1. Host Configuration Variables.........................47 6.3.1. Host Configuration Variables.........................47
6.3.2. Host Variables.......................................47 6.3.2. Host Variables.......................................47
6.3.3. Interface Initialization.............................48 6.3.3. Interface Initialization.............................48
6.3.4. Processing Received Router Advertisements............48 6.3.4. Processing Received Router Advertisements............48
6.3.5. Timing out Prefixes and Default Routers..............51 6.3.5. Timing out Prefixes and Default Routers..............51
6.3.6. Default Router Selection.............................51 6.3.6. Default Router Selection.............................51
6.3.7. Sending Router Solicitations.........................52 6.3.7. Sending Router Solicitations.........................52
7. ADDRESS RESOLUTION AND NEIGHBOR UNREACHABILITY DETECTION.......54 7. ADDRESS RESOLUTION AND NEIGHBOR UNREACHABILITY DETECTION.......53
7.1. Message Validation........................................54 7.1. Message Validation........................................54
7.1.1. Validation of Neighbor Solicitations.................54 7.1.1. Validation of Neighbor Solicitations.................54
7.1.2. Validation of Neighbor Advertisements................55 7.1.2. Validation of Neighbor Advertisements................55
7.2. Address Resolution........................................55 7.2. Address Resolution........................................55
7.2.1. Interface Initialization.............................56 7.2.1. Interface Initialization.............................56
7.2.2. Sending Neighbor Solicitations.......................56 7.2.2. Sending Neighbor Solicitations.......................56
7.2.3. Receipt of Neighbor Solicitations....................57 7.2.3. Receipt of Neighbor Solicitations....................57
7.2.4. Sending Solicited Neighbor Advertisements............58 7.2.4. Sending Solicited Neighbor Advertisements............58
7.2.5. Receipt of Neighbor Advertisements...................59 7.2.5. Receipt of Neighbor Advertisements...................59
7.2.6. Sending Unsolicited Neighbor Advertisements..........61 7.2.6. Sending Unsolicited Neighbor Advertisements..........60
7.2.7. Anycast Neighbor Advertisements......................62 7.2.7. Anycast Neighbor Advertisements......................62
7.2.8. Proxy Neighbor Advertisements........................62 7.2.8. Proxy Neighbor Advertisements........................62
7.3. Neighbor Unreachability Detection.........................63 7.3. Neighbor Unreachability Detection.........................63
7.3.1. Reachability Confirmation............................63 7.3.1. Reachability Confirmation............................63
7.3.2. Neighbor Cache Entry States..........................64 7.3.2. Neighbor Cache Entry States..........................64
7.3.3. Node Behavior........................................65 7.3.3. Node Behavior........................................65
8. REDIRECT FUNCTION..............................................67 8. REDIRECT FUNCTION..............................................67
8.1. Validation of Redirect Messages...........................67 8.1. Validation of Redirect Messages...........................67
8.2. Router Specification......................................68 8.2. Router Specification......................................68
8.3. Host Specification........................................69 8.3. Host Specification........................................69
9. EXTENSIBILITY - OPTION PROCESSING..............................70 9. EXTENSIBILITY - OPTION PROCESSING..............................70
10. PROTOCOL CONSTANTS............................................72 10. PROTOCOL CONSTANTS............................................71
11. SECURITY CONSIDERATIONS.......................................73 11. SECURITY CONSIDERATIONS.......................................73
11.1 Threat analysis............................................73 11.1 Threat analysis............................................73
11.2 Securing Neighbor Discovery messages.......................74 11.2 Securing Neighbor Discovery messages.......................74
12. RENUMBERING CONSIDERATIONS....................................75 12. RENUMBERING CONSIDERATIONS....................................75
IANA CONSIDERATIONS................................................76 IANA CONSIDERATIONS................................................76
REFERENCES.........................................................77 REFERENCES.........................................................77
Authors' Addresses.................................................79 Authors' Addresses.................................................79
APPENDIX A: MULTIHOMED HOSTS.......................................80 APPENDIX A: MULTIHOMED HOSTS.......................................80
APPENDIX B: FUTURE EXTENSIONS......................................81 APPENDIX B: FUTURE EXTENSIONS......................................81
APPENDIX C: STATE MACHINE FOR THE REACHABILITY STATE...............82 APPENDIX C: STATE MACHINE FOR THE REACHABILITY STATE...............82
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used as a destination address, but may be used as a used as a destination address, but may be used as a
source address if the sender does not (yet) know its source address if the sender does not (yet) know its
own address (e.g., while verifying an address is unused own address (e.g., while verifying an address is unused
during stateless address autoconfiguration [ADDRCONF]). during stateless address autoconfiguration [ADDRCONF]).
The unspecified address has a value of 0:0:0:0:0:0:0:0. The unspecified address has a value of 0:0:0:0:0:0:0:0.
Note that this specification does not strictly comply with the Note that this specification does not strictly comply with the
consistency requirements in [ADDR-SEL] for the scopes of source and consistency requirements in [ADDR-SEL] for the scopes of source and
destination addresses. It is possible in some cases for hosts to use destination addresses. It is possible in some cases for hosts to use
a source address of a larger scope than the destination address in a source address of a larger scope than the destination address in
the IPv6 header the IPv6 header.
2.4. Requirements 2.4. Requirements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [KEYWORDS]. document, are to be interpreted as described in [KEYWORDS].
This document also makes use of internal conceptual variables to This document also makes use of internal conceptual variables to
describe protocol behavior and external variables that an describe protocol behavior and external variables that an
implementation must allow system administrators to change. The implementation must allow system administrators to change. The
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Router Solicitation: When an interface becomes enabled, hosts may Router Solicitation: When an interface becomes enabled, hosts may
send out Router Solicitations that request routers to send out Router Solicitations that request routers to
generate Router Advertisements immediately rather than generate Router Advertisements immediately rather than
at their next scheduled time. at their next scheduled time.
Router Advertisement: Routers advertise their presence together Router Advertisement: Routers advertise their presence together
with various link and Internet parameters either with various link and Internet parameters either
periodically, or in response to a Router Solicitation periodically, or in response to a Router Solicitation
message. Router Advertisements contain prefixes that message. Router Advertisements contain prefixes that
are used for determining whether an another address are used for determining whether another address
shares the same link (on-link determination) and/or shares the same link (on-link determination) and/or
address configuration, a suggested hop limit value, etc. address configuration, a suggested hop limit value, etc.
Neighbor Solicitation: Sent by a node to determine the link-layer Neighbor Solicitation: Sent by a node to determine the link-layer
address of a neighbor, or to verify that a neighbor is address of a neighbor, or to verify that a neighbor is
still reachable via a cached link-layer address. still reachable via a cached link-layer address.
Neighbor Solicitations are also used for Duplicate Neighbor Solicitations are also used for Duplicate
Address Detection. Address Detection.
Neighbor Advertisement: A response to a Neighbor Solicitation Neighbor Advertisement: A response to a Neighbor Solicitation
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logical interface having multiple link-layer addresses. logical interface having multiple link-layer addresses.
Neighbor Discovery allows a router to perform Load balancing Neighbor Discovery allows a router to perform Load balancing
for traffic addressed to itself by allowing routers to omit for traffic addressed to itself by allowing routers to omit
the source link-layer address from Router Advertisement the source link-layer address from Router Advertisement
packets, thereby forcing neighbors to use Neighbor packets, thereby forcing neighbors to use Neighbor
Solicitation messages to learn link-layer addresses of Solicitation messages to learn link-layer addresses of
routers. Returned Neighbor Advertisement messages can then routers. Returned Neighbor Advertisement messages can then
contain link-layer addresses that differ depending on, e.g., contain link-layer addresses that differ depending on, e.g.,
who issued the solicitation. This specification does not who issued the solicitation. This specification does not
support a mechanism that allows hosts to Load-balance define a mechanism that allows hosts to Load-balance
incoming packets. incoming packets. See [LD-SHRE].
Anycast addresses - Anycast addresses identify one of a set of Anycast addresses - Anycast addresses identify one of a set of
nodes providing an equivalent service, and multiple nodes on nodes providing an equivalent service, and multiple nodes on
the same link may be configured to recognize the same Anycast the same link may be configured to recognize the same Anycast
address. Neighbor Discovery handles anycasts by having nodes address. Neighbor Discovery handles anycasts by having nodes
expect to receive multiple Neighbor Advertisements for the expect to receive multiple Neighbor Advertisements for the
same target. All advertisements for anycast addresses are same target. All advertisements for anycast addresses are
tagged as being non-Override advertisements. A non-Override tagged as being non-Override advertisements. A non-Override
advertisement is one that does not replace the information advertisement is one that does not update or replace the
sent by another advertisement. These advertisements are information sent by another advertisement. These
discussed later in the context of Neighbor advertisement advertisements are discussed later in the context of Neighbor
messages. This invokes specific rules to determine which of advertisement messages. This invokes specific rules to
potentially multiple advertisements should be used. determine which of potentially multiple advertisements should
be used.
Proxy advertisements - A node willing to accept packets on behalf Proxy advertisements - A node willing to accept packets on behalf
of a target address that is unable to respond to Neighbor of a target address that is unable to respond to Neighbor
Solicitations can issue non-Override Neighbor Advertisements. Solicitations can issue non-Override Neighbor Advertisements.
Proxy advertisements are used by Mobile IPv6 home Agents to Proxy advertisements are used by Mobile IPv6 home Agents to
defend mobile nodes' addresses when they move off-link. defend mobile nodes' addresses when they move off-link.
However, it is not intended as a general mechanism to handle However, it is not intended as a general mechanism to handle
nodes that, e.g., do not implement this protocol. nodes that, e.g., do not implement this protocol.
3.1. Comparison with IPv4 3.1. Comparison with IPv4
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Neighbor Discovery supports links with different properties. In the Neighbor Discovery supports links with different properties. In the
presence of certain properties only a subset of the ND protocol presence of certain properties only a subset of the ND protocol
mechanisms are fully specified in this document: mechanisms are fully specified in this document:
point-to-point - Neighbor Discovery handles such links just like point-to-point - Neighbor Discovery handles such links just like
multicast links. (Multicast can be trivially multicast links. (Multicast can be trivially
provided on point-to-point links, and interfaces provided on point-to-point links, and interfaces
can be assigned link-local addresses.) can be assigned link-local addresses.)
multicast - Neighbor Discovery supports multicast capable multicast - Neighbor Discovery operates over multicast capable
links as described in this document. links as described in this document.
non-broadcast multiple access (NBMA) non-broadcast multiple access (NBMA)
- Redirect, Neighbor Unreachability Detection and - Redirect, Neighbor Unreachability Detection and
next-hop determination should be implemented as next-hop determination should be implemented as
described in this document. Address resolution, described in this document. Address resolution,
and the mechanism for delivering Router and the mechanism for delivering Router
Solicitations and Advertisements on NBMA links is Solicitations and Advertisements on NBMA links is
not specified in this document. Note that if not specified in this document. Note that if
hosts support manual configuration of a list of hosts support manual configuration of a list of
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information option). It also assists with address information option). It also assists with address
autoconfiguration as specified in [ADDRCONF], for autoconfiguration as specified in [ADDRCONF], for
which there may be more restrictions on the prefix which there may be more restrictions on the prefix
length. length.
L 1-bit on-link flag. When set, indicates that this L 1-bit on-link flag. When set, indicates that this
prefix can be used for on-link determination. When prefix can be used for on-link determination. When
not set the advertisement makes no statement about not set the advertisement makes no statement about
on-link or off-link properties of the prefix. In on-link or off-link properties of the prefix. In
other words, if the L flag is not set a host MUST other words, if the L flag is not set a host MUST
NOT assume that an address derived from the prefix NOT conclude that an address derived from the
is on-link unless it is explicitly told in another prefix is off-link. That is, it MUST NOT update a
message (e.g. Redirect). For instance, the prefix previous indication that the address is on-link.
might be used for address configuration with some
of the addresses belonging to the prefix being on-
link and others being off-link.
A 1-bit autonomous address-configuration flag. When A 1-bit autonomous address-configuration flag. When
set indicates that this prefix can be used for set indicates that this prefix can be used for
stateless address configuration as specified in stateless address configuration as specified in
[ADDRCONF]. [ADDRCONF].
Reserved1 6-bit unused field. It MUST be initialized to zero Reserved1 6-bit unused field. It MUST be initialized to zero
by the sender and MUST be ignored by the receiver. by the sender and MUST be ignored by the receiver.
Valid Lifetime Valid Lifetime
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http://www.ietf.org/ipr. http://www.ietf.org/ipr.
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Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2007). This document is subject Copyright (C) The IETF Trust (2007). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Disclaimer of Validity Disclaimer of Validity
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
This Internet-Draft expires June, 2007. This Internet-Draft expires September, 2007.
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